1. Field of the Invention
This invention relates to a mower unit attachable to a vehicle body and including a mower deck having a top board and one front wall and one side wall depending from the top board. The mower deck defines a grass discharge opening opposed to the side wall, and contains a plurality of rotary blades arranged side by side to be rotatable about vertical axes. All these rotary blades are rotatable in the same direction so that the front half, with respect to a traveling direction of the vehicle, of a rotating track of each blade points toward the side defining the grass discharge opening.
2. Description of the Related Art
In a mower unit of the type noted above, as disclosed in Japanese Patent Publication (Unexamined) No. 8-280225, for example, the top board of the mower deck has a front portion arched to define a tunnel therein extending to the grass discharge opening at one side of the deck. Grass clippings flying from the front half of the rotating track of each rotary blade are transported along the tunnel to the grass discharge opening. Such a mower unit is known as the side discharge type and is in wide use.
A mulching operation is sometimes required to cut grass clippings into minute pieces (mulch) and leave them along swaths in order to make a collection of grass clippings unnecessary and to utilize the grass clippings as compost. For this purpose, as disclosed in Japanese Patent Publication (Unexamined) No. 6-14634, a proposal has been made to provide mulching baffles inside the mower deck to define a mulching chamber (enclosure) for each rotary blade.
The above-noted mower deck having a tunnel for transporting grass clippings is capable of transporting the grass clippings smoothly and promptly along the tunnel, with little chance of the grass clippings entrained by the rotary blades. This mower deck has an advantage of cutting tall grass or lawn in a neglected condition, with little power loss due to the clippings being entrained by the rotary blades. However, this mower deck is ill-suited for an operation to cut only upper part of grass under good care, and discharge and scatter the clippings evenly in an inconspicuous way.
When a mulching operation is carried out by using the mower deck with a tunnel, mulching chambers are formed by installing baffles rearwardly of the tunnel, i.e. in regions of small depth. It is difficult to retain grass clippings in the mulching chambers for a sufficiently long time. It is thus difficult to secure a long mulching time for improved mulching efficiency.
Further, U.S. Pat. Nos. 5,845,475 and 5,987,863 disclose mower units of the side discharge type convertible to the mulching type by mounting mulching baffles in the mower deck. However, such a mulching mower unit with mulching baffles mounted in the mower deck has a flow control baffle for use in the side discharge remaining fixed, which is inconvenient for a mulching operation.